A Good Night for Sky Gazing

[Update: indeed, both meteors and auroras are visible tonight, at least as far south as Massachusetts, so residents of northern-tier states should definitely be looking!]

Tonight, if the sky is clear and dark in your vicinity, would be a good night for staying up late, going outside, and looking up. Not that it’s an exceptional night for star gazing, necessarily; I wrote “sky-gazing” for a reason. The two phenomena you’re most likely to see are much, much closer than the stars. Both occur in the Earth’s upper atmosphere, and are generated by effects that occur within the solar system (i.e., the Sun, its planets, and their neighborhood.)

The phenomena in question? Meteors, for sure; and auroras, just maybe.

Tonight you will definitely see an unusually large number of meteors (a.k.a. “shooting ‘stars’ “) from the annual Perseid meteor shower. Ordinary meteors are dust-grains and pebbles flying through the solar system that happen to hit the Earth. When these objects enter the Earth’s atmosphere at high speed, they heat up and glow brightly, leaving a track across the sky until they evaporate away entirely. The dust and small rocks are debris from comets, themselves balls of rock, dirt and ice, typically a few miles (kilometers) across, that orbit the Sun on trajectories that are far more elongated than the Earth’s near-circular path. You’ll see more meteors after midnight, but before midnight, the ones you see will often show long trails. However, the moon will drown some of them out before it sets, roughly one hour before midnight; try to go out after moonset if you can. (Meteors will continue to be common for an additional two or three nights, though the number will tend to decrease over time.)

You might also see auroras (a.k.a. the “northern” or “southern ” lights); there’s a moderate chance of them tonight, the more so the higher your latitude. Auroras arise when solar storms create clouds of subatomic particles that cross from the Sun to the Earth. Some of these electrically-charged subatomic particles are steered by the Earth’s magnetic field toward the Earth’s magnetic poles, and when the particles enter the atmosphere, they strike atoms, causing the atoms to glow. The colors seen most often green or red. Last week I wrote about how you can try to guess when they may be occurring. The moon, again, will drown out the colors, so look after moonset, an hour before midnight in most places.

This is not to dismiss actual star gazing. We’re still waiting for stellar event that should be visible to the naked eye: a minor star explosion known as a nova that has been predicted, with moderate confidence, to occur in the next month or so. (But… don’t be too terribly surprised if it is delayed, or doesn’t occur at all. The prediction is empirical and based only on three previous occurrences — and nature doesn’t always follow simple patterns.) I’ve written about this event here.

Again, just to reemphasize: for all of these, you need dark skies! You will barely see anything (except the brightest meteors) from a city, or even from a suburb with parking-lot lights nearby. Get as far from lights as you can — stay away from busy roads where headlights will periodically blind you — and let your eyes adjust to the darkness.

Now here’s something worth contemplating.

• Meteors and auroras typically occur 50-200 miles (100-300 km) overhead — no further than the distance from Boston to New York or from London to Paris.
• The nova explosion, if it occurs, will be more than 10,000,000,000,000,000 miles (km) overhead — a hundred million times further than the Sun is from Earth.

But they’re comparably bright. Just to keep things in perspective.